Method and apparatus for heating a catalytic converter to reduce emissions

ABSTRACT

A mixture of hydrogen and air is introduced onto the face of the catalytic monolith of a catalytic converter in the exhaust line of a cold internal combustion engine. The hydrogen spontaneously combusts, thereby pre-heating the catalytic converter. Pre-heating the catalytic converter significantly improves the effectiveness of the catalytic converter in eliminating undesirable emissions of the internal combustion engine. The hydrogen is preferably produced on-board the vehicle using the system. The hydrogen source may also be coupled to the internal combustion engine to be burned by the engine during startup in the absence of gasoline to minimize the production of unacceptable emissions while the catalyst is brought up to light-off temperature.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to the field of catalysis forthe reduction of emissions from internal combustion engines. Moreparticularly, the present invention relates to a method and apparatusfor heating a catalyst by spontaneous combustion of hydrogen introducedinto the catalyst. More particularly still, the present inventionrelates to the conditioning through preheating of a standard three-wayor two-way catalytic monolith in a vehicle powered by an internalcombustion engine, such as an automobile.

The control and suppression of unwanted emissions created by theoperation of an internal combustion engine is a primary considerationfor engine designers and vehicle manufacturers because of nearlyworld-wide governmental requirements regarding acceptable emissionlevels. Over eighty percent (80%) of the unacceptable emissions orpollutants created by internal combustion engines equipped withcatalytic converters occur during cold start operations. Thesepollutants are emitted for a period of one to three minutes after coldengine starting, in large part because that is the time period requiredfor the catalyst to reach an efficient operating temperature. Therefore,even though the engine exhaust is flowing through the catalyticconverter, until the exhaust heats the catalytic converter to itsoperating range from engine start up, the exhaust flow is only slightlycatalyzed during that time period.

In order to meet governmental emission standards for internal combustionengine exhaust, a catalytic converter is located in the exhaust streamof the engine. The converter typically includes a canister holding asuitable catalyst, such as a three-way catalytic converter (TWC)catalyst monolith, that will oxygenate unburned, unacceptable componentsin the exhaust stream including hydrocarbons ("HC"), their partiallyoxidized derivatives such as aldehydes and carbon monoxide ("CO"), andat the same time reducing nitrogen oxides ("NO_(x) "), after almoststoichiometric fuel burn with oxygen in the cylinders of the engine. Theexhaust gas is passed through the catalyst monolith, thereby completingthe oxygenation of unburned HC and CO, and the reduction of NO_(x) inthe exhaust to convert these unacceptable emissions into acceptableemissions. Certain unacceptable emissions in the exhaust stream,including unburned hydrocarbons and carbon monoxide, require anoxidation reaction to destroy them so that they end up as thecorresponding oxides, e.g. water and carbon dioxide. On the other hand,NO_(x) requires a reduction reaction to develop N₂ and O₂. In fact, theO₂ product of this reduction contributes to the oxidation of the HC andCO in the exhaust.

TWC catalysts are currently formulated and designed to be effective overa specific operating range of both lean and rich fuel/air conditions anda specific operating temperature range. These particulate catalystcompositions enable optimization of the conversion of HC, CO, andNO_(x). This purification of the exhaust stream by the catalyticconverter is dependent on the temperature of the exhaust gas and thecatalytic converter works optimally at an elevated temperature,generally at or above 300° C. The time span between when the exhaustemissions begin (i.e., "cold start"), until the time when the substrateheats up sufficiently for the catalyst to work efficiently, is generallyreferred to as the light-off time. Light-off temperature is generallydefined as the temperature at which fifty percent (50%) of the emissionsfrom the engine are being converted as they pass through the catalyst.

The conventional method of heating the catalytic converter is to heatthe catalyst by contact with high temperature exhaust gases from theengine. This heating, in conjunction with the exothermic nature of theoxidation reaction occurring at the catalyst, will bring the catalyst tolight-off temperature. However, until the light-off temperature isreached, the exhaust gas passes through the catalyst relativelyunchanged. In addition, the composition of the engine exhaust changes asthe engine heats from the cold start temperature, and the catalyst isdesigned to work best with the composition of the exhaust stream presentat the normal elevated engine operating temperature.

There have been several attempts to shorten or avoid the time betweencold start and light-off of the catalytic converter. Current techniquesemploy one or more of the following methods: electrical heating of theexhaust gases and/or of the catalytic converter itself; thermalinsulation; multi-chambered configurations of the catalytic converter;and/or placing the catalytic converter adjacent to the engine forheating. All of these methods have drawbacks and limitations.

Placing the catalytic converter almost immediately adjacent to theengine is not feasible because of the tendency to overheat the catalystwith resulting accelerated degradation of the catalyst due to excessiveheat. Thermal insulation is also not an acceptable option because of thesame problems, especially during operation under maximum operatingtemperature ranges.

Electrical heating of catalytic converters ("EHC") has been a popularproposed method of attempting to preheat the catalyst monoliths.Limitations on the equipment and process, however, affect the utility ofthis method. The primary limitation on electrical preheating is theelectrical energy required by the heater. The typical car battery is nota practical power source to supply the electrical power because theelectrical load on the vehicle battery during the period required mayexceed the rated battery output. In any event, the load placed on atypical 12 volt vehicle battery will shorten the lifetime of thebattery. Also, there is a measurable delay between the time the operatorof the vehicle places the ignition switch in the "on" position and thetime the heater brings the catalyst to light-off temperature.

Typically, in the interval between start up and light-off, the exhauststream is oxygen deficient. Because the catalyst requires oxygen tocomplete the catalytic reaction, supplemental air must be blown over thecatalyst. Even when using a secondary air flow to overcome oxygendeficiency, the secondary air flow must be closely controlled to avoidan excess of oxygen, in which case the catalytic converter is lesseffective in reducing NO_(x). However, it should be noted that NO_(x)contributes a very small portion of unacceptable emissions when anengine is cold; most of the emissions that must be dealt with compriseHC and CO and the like.

An alternative to battery powered electrical heating has been todecrease the strain on the power supply by supplying the power directlyfrom an alternator rather than directly from the vehicle battery. Analternator powered, electrically heated catalyst ("APEHC") stillrequires a 5 to 10% increase in battery capacity to cope with the EHCstart-up scenario. Even with the APEHC system, there still is a concernwith respect to battery capacity because electric heating is needed foran extended period of time, i.e., more than 25-30 seconds. In addition,the maximum alternator power output required in the APEHC systemrequires a complicated switching mechanism and an altered alternatorspeed between 3,000 and 4,500 rpm during the heat up time period, andthe alternator must be oversized.

The multi-chamber configurations of catalytic converters generallyconform to one of two theories. In one multi-chamber configuration, asmall portion of catalyst known as a "starter catalyst" is positionedupstream from the primary catalyst. This "starter catalyst" is generallycloser to the exhaust manifold. This location, in conjunction with asmaller thermal mass associated with its smaller size, causes thecatalyst to heat much more quickly than a single catalyst. Thisconfiguration, however, is generally unacceptable because the startercatalyst in the exhaust stream creates a higher back pressure whichreduces the overall engine efficiency and robs the engine of poweroutput.

Another method of providing multiple chambers in the exhaust flowincludes a first catalyst having low temperature characteristics usedonly during cold start conditions, and, after the catalyst temperatureranges rise to a selected elevated level, the exhaust gas flow isswitched to pass through the conventional catalytic converterconfiguration. A variation of this approach is to run all cold startemissions through a separate absorber (such as zeolite or a metalsieve-type substance) wherein unacceptable emissions are captured andlater released back into the exhaust stream. This method, however, isimpractical because of the complicated switching mechanism used todivert flow to the absorber, the size and space requirements of theabsorber, and the impracticality of releasing the unacceptable emissionsfrom the absorber back into the exhaust stream.

Finally, one method runs the engine excessively rich in the cold startcondition and ignites the resulting super-rich mixture to directly heatthe catalyst. This approach has proved wholly unreliable and has otherserious drawbacks, including reduced engine and catalyst life.

To date, there has not been a catalytic converter heating system whichgives almost instantaneous heating of the catalytic converter withoutthe inherent drawbacks stated above.

Thus, there remains a need for an improved catalytic converter systemthat reduces ineffective catalytic action immediately after coldstart-up of an engine. Such a system must be simple and must not reducethe rated lifetime of the engine, the catalytic converter, or thebattery components of the vehicle.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a method and apparatus forreducing undesirable emissions from an internal combustion engine byusing a gas that spontaneously combusts in the presence of a catalyst toheat the catalyst into its operating range in a minimal amount of time.In a preferred embodiment, the catalyst is heated by providing acontrolled flow of hydrogen and a source of oxygen, such as air, intothe exhaust line or pipe, preferably at a point between the enginemanifold and the catalytic converter. The hydrogen combusts with theoxygen in the presence of the catalyst to produce water. This exothermiccombustion provides localized heat at the catalyst which raises thetemperature of the catalyst material.

The hydrogen is preferably supplied from an electrolyzer on board thevehicle which is supplied with DC power from the vehicle's alternatorvia an AC/DC converter. Such an electrolyzer produces hydrogen andoxygen from water. The oxygen so produced is vented while the hydrogenis accumulated during non-cold engine operations for release duringengine start up and cold operating conditions. Sufficient hydrogen maybe stored in a hydride such as LaNi₅ or FeTi or may be accumulated in apressure tank or other container such that there is hydrogen for severalstarts. The source of water may be distilled water; however, windshieldwasher fluid may also be used to eliminate the need for another storagefacility for water.

It is well recognized by those of skill in the art of catalyticconverter design that some monolith compositions more quickly and easilyreach light-off temperatures than others. Consequently, the presentinvention is especially advantageous when applied to catalysts that aredifficult to bring to light-off temperature by applying a small layer orfilm of a material that, is more reactive to hydrogen and is thus morerapidly heated by spontaneous combustion of hydrogen. Such a layer orfilm could be applied to a face of the slow-heating monolith or could bedistributed throughout the converter, as design requirements dictate.Rapid exothermic heating of the applied catalyst quickly brings theentire structure to a temperature at which normal, efficient catalyticaction occurs.

In another preferred embodiment of the invention, a small amount ofstored hydrogen may be supplied to the fuel injection system of thevehicle to assist in cold starts. This allows instant firing of theengine, even with fuels with low vapor pressure, such as methanol,ethanol, or low Reid vapor pressure gasoline.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the invention will becomeapparent from the following description when read in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a schematic diagram of the apparatus of the present inventionfor heating a catalytic converter;

FIG. 2 is an exploded view of a preferred electrolyzer that may beemployed in the present invention;

FIG. 3 is a schematic of a hydrogen capturing and handling detail of thesystem of the present invention;

FIG. 4 is a schematic of a test setup to assist in the determination ofthe ideal parameters of a system functioning in accordance with theteachings of the present invention;

FIG. 5 is a sectional view of a simplified representation of a catalyticconverter monolith showing air and hydrogen flow in the axial direction;

FIGS. 5A, 5B, 5C, 5D, and 5E are temperature plots of the variation oftemperature with time along the axial length of a catalytic convertermonolith for different hydrogen concentrations in a flowing gas stream;

FIG. 6 is a sectional view of a simplified representation of a catalyticconverter monolith for temperature measurements along the major radialdirection in the monolith;

FIGS. 6A, 6B, 6C, 6D, and 6E are temperature plots of the variation oftemperature with time along the major radial direction of a catalyticconverter monolith for different hydrogen concentrations in a flowinggas stream; and

FIG. 7 is a schematic diagram of the apparatus of the present inventiondepicting a system for the combustion of hydrogen for cold startupassist for an internal combustion engine.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides a method and apparatus for thermallyconditioning a catalyst in order to enhance the conversion ofunacceptable emissions emanating from an internal combustion engine intowater and other acceptable emissions.

Referring first to FIG. 4, the schematic depicts the generalconfiguration of a conditioning system 10 for catalytically enhancingemission reactions. The system 10 includes a catalytic converter 11, ametered hydrogen supply 13, and a metered air supply 14. Additionally,one or more thermocouples 11a are implanted at various positions alongthe radial and axial directions of the catalytic converter. Thethermocouples are connected to a data logger 12, capable of recordingthe temperature of the catalyst as a function of time. The system 10 ofFIG. 4 is particularly useful in demonstrating the efficacy of thepresent invention and for determining the optimum flow rates of hydrogenand air and other system parameters.

The flows of hydrogen and air from supplies 13 and 14 are controlled byvalves or regulators 15 and 16, respectively. The regulator 16, whichcontrols the air supply, is preferably coupled to a rotameter 17, whichmeasures the air flow rate. The metered air then flows to a mixingchamber 20. The flow of hydrogen, which is controlled through a valve orregulator 15 and regulated by an electronically controlled mass flowcontroller 18 in conjunction with the controller 19, is also deliveredto the mixing chamber 20.

In the mixing chamber 20, the hydrogen and air are thoroughly mixedbefore passing through a three way valve 21. The three way valve 21operates to provide a bypass of the hydrogen and air mixture directly tothe surrounding environment via an outlet 23 or to a conduit 22, throughwhich the hydrogen and air mixture are introduced into the catalyticconverter 11. This configuration allows for a widely varying flow ofhydrogen and air to a catalytic converter to determine the properhydrogen/air ratios for practicing the present invention.

FIG. 5 depicts a catalytic converter monolith 30 in the catalyticconverter 11 that may be conditioned with the present invention. Arrows40 represent the stream of air and hydrogen passing through conduit 22and into contact with the monolith 30 along a central axis 37. Points31a, 31b, 31c, 31d, and 31e represent the location of thermocoupleprobes, as generally represented by 11a in FIG. 4, for the measurementof temperatures along the axial or flow direction into the catalyticconverter.

FIG. 6 depicts the radial distribution of a plurality of probes 33a,33b, and 33c within the monolith 30. Below are listed some results forvariously changing parameters as determined by the distribution of thethermocouple probes 31a-31e and 33a-33c.

FIGS. 5A-D, inclusive, depict test results of the distribution oftemperatures detected by the thermocouples distributed as shown in FIG.5 for varying concentrations of hydrogen. Similarly, FIGS. 6A-D,inclusive, depict test results of the distribution of temperaturesdetected by the thermocouples distributed as shown in FIG. 6 for thesame concentrations of hydrogen. These plots clearly show theeffectiveness of the heating on the face of the catalytic convertermonolith and will assist those of skill in the art in selecting optimumfluid flow rates in a particular application.

FIG. 1 shows an overall system of the present invention. In this system,the catalytic converter 11 is located in an exhaust line 42 from avehicle's exhaust manifold, as shown. The exhaust line 42 is providedwith air from an air pump 44 and hydrogen from a hydrogen inlet line 46.The air pump could be any suitable air source, such as a receiver, forinjecting air into the exhaust line at suitable pressure and volumetricflow rate to achieve the ideal air/hydrogen ratio mixture.

The hydrogen source portion of the system of FIG. 1 provides anotherfeature of the present invention. The major components of the systeminclude a reservoir 48, an electrolyzer 50, and a hydrogen storagecylinder 52. As shown in FIG. 1, the electrolyzer 50 may preferablycomprise a plurality of stacked identical cells 51. The reservoir 48serves both as a water reservoir and as a separator for oxygen andwater. In a preferred embodiment, the reservoir 48 may be a vehicle'swindshield washer fluid storage container. A port 54 permits theintroduction of water into the reservoir and also serves as a vent toatmosphere for oxygen. Water flows by gravity drain or is pumped fromthe reservoir 48 to the electrolyzer 50 via a drain line 56. As theelectrolyzer develops hydrogen and oxygen, the oxygen and entrainedwater flows naturally back to the reservoir 48 via a return line 58.

The next major component of the hydrogen source is the electrolyzer 50,shown in greater detail in FIG. 2. In the following description of theelectrolyzer 50, the materials of construction referred to as"preferred" are the materials actually used in a test device to provethat the invention would work for its intended purpose. In commercialproduction models of the present invention, where possible, lessexpensive materials will be used throughout, such as carbon steel fortitanium where possible, and plastic such as polypropylene where heatand stress will permit the use of such material.

The electrolyzer 50 may be referred to herein as a proton exchangemembrane (PEM) electrolyzer 50. The proton exchange membrane itself mayprove corrosive in this environment in contact with certain substances,thus requiring the careful selection of the materials of construction ofthe electrolyzer. For example, the PEM should only contact carbon orgraphite. However, those of skill in the art will readily recognizewhere less exotic materials than those listed in the followingdiscussion that are located away from the PEM material itself and theoxygen electrode catalyst can be readily employed without penalty. Forexample, graphite will be the material of choice in certain structuralelements, and not some obvious candidates such as copper, aluminum, oriron, which can corrode thus forming ions that can poison the oxygenand/or hydrogen electrode catalysts.

The PEM electrolyzer 50, formed as a stack as shown in FIG. 2, includesa pair of endplates 60 and 62. The endplates 60 and 62 are preferablytitanium and measure 4.2"×4.2"×3/4". Adjacent the top endplate 60 is ananodic cell frame 64. The cell frame 64 is preferably a carbonfiber-filled Teflon sheet, sold under the trademark Zymaxx by Du Pont.The cell frame 64 retains a 1:1 molar ratio of iridium and rutheniumdioxides (IrO₂ /RuO₂) as the anodic electrocatalyst. The cell frame 64also includes a plurality of flow ports 66 to permit the supply ofreactant (water) and/or removal of electrolysis products (hydrogen oroxygen gases). Below the cell frame 64 is an expanded titanium metalcurrent collector (flow field) 68, preferably 25 Ti 40-3/32 from ExmetCorp. An anode substrate 70 is preferably a porous titanium platemeasuring 2.49"×2.49"×0.05". Below the anode substrate 70 is a protonexchange membrane 72, cut from a sheet of Nafion 117 from Du Pont whichserves as a solid electrolyte material and which is 175 μm thick.

FIG. 2 depicts a gasket 74, one of perhaps several installed whererequired. Gaskets 74 are stamped from 0.033" thick fluorosilicone sheet(Viton) and from 0.005" thick unsintered PTFE sheet. The electrolyzer 50further includes a cathode substrate 76 like the anode substrate 70 andan expanded titanium flow field 78 like the titanium flow field 68.

Finally, the PEM electrolyzer 50 includes a cathodic cell frame 80formed of polychlorotrifluoroethylene (PCTFE) sheet, sold under thetrademark KEL-F by Afton Plastics. The cathodic cell frame 80 retains afuel cell gas diffusion electrode containing high surface area colloidalplatinum, supported on platinum black, having a platinum loading of 4.0mg/cm² as the cathodic electrocatalyst layer.

As shown in FIG. 2, the various components of the PEM electrolyzer arestacked together and retained with a plurality of tie rods 82,preferably 16 such tie rods. Stainless steel tubing, such as SS316, arethen screwed into four threaded ports on one of the titanium endplates.These ports are the water inlet port 56, the oxygen outlet port 58, anda pair of hydrogen outlet ports 84. To minimize electrical contactresistances, the titanium endplates 60 and 62 and the expanded titaniummetal current collectors 68 and 78 may be electroplated with a thin filmof gold.

The cathode and the anode of the electrolyzer are of specialconstruction. The cathodic electrode structure for hydrogen evolution isfashioned from commercially available fuel cell gas diffusion electrodesfrom E-TEK of Natick, Mass. This structure comprises a hydrophobic gasdiffusion layer on a carbon cloth backing, which acts as a support forthe active hydrophilic electrocatalyst layer. This active layer containshigh surface area colloidal platinum (˜100 m² /g), supported on carbonblack (60 wt % Pt on C), yielding a platinum loading of 4.0 mg/cm². Thecathodic electrode structure, having an area of 40 cm², was hot-pressedonto one side of a segment of precleaned Nafion 117 PEM material.Hot-pressing was carried out between the plates of a hot-press, elevatedto 200° C. for 60 seconds, and using a force of 15,000 pounds.

For the anodic electrocatalyst layer, a 1:1 molar ratio of iridium andruthenium chlorides are dissolved in ca. 8 ml of concentrated HCl andheated to almost dryness. The resulting chlorides are then dissolved inisopropanol to make an ink-like coating. A porous titanium plate, 0.05"thick, of about 50% porosity, made from sintered titanium spheres ofabout 0.005" in diameter from Astro Met of Cincinnati, Ohio, is etchedin 12% HBF₄ for 60 seconds and rinsed with isopropanol. This substrateis then coated with the ink-like mixture and the solvent evaporatedunder low heat of about 90° C. The coating and drying procedure isrepeated seven times, then the electrode is heated in a furnace at 400°C. for 10 minutes in ambient air. The coating, drying and furnacetreatment is repeated twice more, but with a final baking time of twohours instead of 10 minutes.

Returning to FIG. 1, in addition to the reservoir 48 and theelectrolyzer 50, the system includes a hydrogen storage cylinder andvarious supporting components. These components include a liquid watertrap 86 to eliminate most of the entrained water from the hydrogen fromthe electrolyzer, a solenoid valve 88 to blow out the trap, a checkvalve 90, and a pressure relief valve 92 to protect the system againstoverpressurization. FIG. 3 depicts additional details and a preferredarrangement of the hydrogen gas handling and capture system.

As previously described, the electrolyzer 50 includes a proton exchangemembrane in its stacked construction so that generated oxygen is ventedto the water source reservoir and the hydrogen generated can beaccumulated at pressure. Prior to operation, the system of FIG. 3permits purging with an inert gas, such as nitrogen. For safety reasons,all air is first removed from the system by attaching a nitrogen gasfeedline at a purge gas inlet 94 downstream of a check valve 90. Duringthe purging operation, the hydrogen storage cylinder or vessel 52,preferably made of a metal hydride, is detached at a quick disconnect96. This operation effectively seals both the vessel 52 and a gas line98, to keep the purge gas out of the vessel 52. The remainder of thesystem is then purged from the purge gas inlet 94 through a backpressure regulator 100.

To charge the system with hydrogen, a needle valve 102 between thestorage vessel 52 and the back pressure regulator 100 is shut. Hydrogengas generated by the electrolyzer is processed through a four-stageprocess to remove entrained water (liquid or vapor) and any oxygencontaminant from the hydrogen stream before storage. The first stepinvolves removal of a small amount of entrained liquid water coming fromthe electrolyzer in the hydrogen gas. This entrained liquid water isremoved without a pressure loss by means of the entrained liquid watertrap 86. The second step involves cooling the hydrogen gas stream fromthe electrolyzer temperature to ambient in a condensing coil 104. Theelectrolyzer is typically at least 20° C. above ambient, with the exacttemperature depending on electrolyzer operating conditions. This secondstep condenses a substantial portion of the water vapor in the hydrogengas stream. This condensed water could absorb a significant amount ofalcohol, which may be present during operation using windshield washerfluid as the electrolyzer reactant feed. The condensate is collected ina condensate collector 106 and removed through a drain valve 108.

At this point, the hydrogen gas stream is still saturated with watervapor, but now at a lower temperature. This saturated gas stream is nextpassed into a zeolite-filled gas drier 110. This drier absorbs watervapor and any alcohol vapor present when using a windshield washer fluidfeed. Any oxygen contaminant present in the hydrogen gas stream is theneliminated in a catalytic recombiner or oxygen eliminator 112 to reduceit to water. Final clean-up of the hydrogen gas stream is accomplishedin a second zeolite absorber bed in a polishing drier 114. The polishingdrier removes traces of water produced by the catalytic recombiner 112.

The hydrogen gas handling system of FIG. 3 is designed for relativelyshort term operation; longer term operations, for example 100,000 miles,would utilize other methods of water removal known in the art. Asatisfactory metal hydride hydrogen storage unit is available fromHydrogen Consultants of Littleton, Colo. Such an available unit canstore 30 liters of hydrogen, which can be delivered at 30-45 psig, withrecharging using hydrogen gas at 100-200 psig.

As previously described, it has been found that the introduction of arelatively small percentage of hydrogen in the air stream of a typicalautomobile gas exhaust provides nearly spontaneous heating of a majorportion of a face 32 (FIG. 5) of the catalyst material almostimmediately following ignition in the internal combustion engineproviding the exhaust gas. This heating along the face 32 of theconverter is fortuitous because it has been found that the mosteffective site for providing local heating is along and near theupstream face 32 of the catalyst monolith 30. In fact, where themonolith 30 is made of a material that heats slowly when used inassociation with the present invention, the face 32 may comprise a morereactive catalytic material to bring the entire catalytic converter tolight-off more quickly.

In addition, the heat supplied by the spontaneous combustion of thehydrogen in the presence of the catalytic converter 30 produces only asmall quantity of water as a product of the reaction, which does notdegrade the performance of the catalytic converter.

A system 10 built in accordance with the present invention as depictedin FIGS. 4, 5, and 6 have provided preferred parameters of air andhydrogen flow. The air flow rate, depending on engine size and tuningparameters, typically falls in the range of 40 to 250 liters per minute(lpm). The ideal range is between 80 and 200 lpm, depending on enginesize. Effective concentrations of hydrogen for these flow rates are oneto twenty-eight volume percent, with a preferred range of five toeighteen percent. The ideal range of hydrogen concentration, againdepending on engine size, has been found to be eight to fifteen percent.For example, at 150 lpm flow rate across the catalytic converter, theideal range for hydrogen concentration in that flow is 12 to 13 volumepercent. Under those conditions, light-off temperature at the face 32 isreached in about one second. At 90 lpm and at 8.5 to 11 volume percenthydrogen, light-off is achieved in about two seconds.

The power consumption at the catalyst varies depending on the flow rateand the concentration of hydrogen. For example, at a flow rate of thirtyto fifty lpm and a concentration of 10-111/2 volume percent hydrogen,the power required to heat the monolith to light-off is approximately1.5 watt hours. Similar results in an EHC unit require approximately 10to 15 watt hours.

The present invention is also suitable for use in low ambienttemperature conditions, as low as -7° C. or lower. Depending on theactive catalyst compositions used, the amount of time required toachieve light-off may double. In those conditions, it may be desirableto add a small electrical heater, which would be much smaller than anEHC heater and require only about 200 watts of power, in order toachieve the results at normal ambient temperatures.

Finally, FIG. 7 depicts an on-board hydrogen ignition assist system ofthe present invention. A source of hydrogen, such as an electrolyzer asbefore or any suitable means, fills the hydrogen storage cylinder 52. Anignition supply line 120 taps off the hydrogen line to a control valve122. The control valve 122 controls the supply of hydrogen into anengine ignition 124. The engine ignition 124 includes the fuel, air, andelectrical components for an internal combustion engine 126. Thus, thehydrogen can be supplied at any convenient location so that it isinjected into the cylinders of the engine 126. For example, hydrogenunder pressure can be supplied to the intake manifold where there isalready a fuel/air mixture (during the inlet cycle), or the hydrogen canbe mixed with air before it goes into the engines fuel injection system,or other means.

The preferred system of FIG. 7 turns the internal combustion engine 126into a hydrogen fuel injected engine for the first few seconds ofstart-up, before any gasoline is introduced into the engine. This way,the catalytic converter can be brought to light-off while the engine isproducing no undesirable emissions. Then, when gasoline is finallyinjected into the system, the catalytic converter is heated to efficientoperating temperature.

Expended fuel gases are collected in an output manifold 128 and flowinto the exhaust line 42. An ignition control 130 provides controlsignals to the control valve 122 for the introduction of hydrogen and tothe engine ignition 124 to coordinate hydrogen introduction during coldstart operations. The on-board hydrogen ignition assist system functionswith or without the catalyst conditioning system but is preferablyincluded with such a system since they may both use the hydrogengeneration and on-board storage.

The principles, preferred embodiment, and mode of operation of thepresent invention have been described in the foregoing specification.This invention is not to be construed as limited to the particular formsdisclosed, since these are regarded as illustrative rather thanrestrictive. Moreover, variations and changes may be made by thoseskilled in the art without departing from the spirit of the invention.

I claim:
 1. A method of heating a catalyst from a cold condition tolight-off temperature for carbon-containing compounds, the methodcomprising the steps of introducing gaseous hydrogen and oxygen to thecatalyst to induce spontaneous exothermic combination of the hydrogenand the oxygen by the catalyst prior to the introduction of reactiveorganic gases or carbon monoxide to the catalyst.
 2. The method of claim1 further comprising the step of storing gaseous hydrogen within ahydrogen storage vessel prior to the step of introducing hydrogen. 3.The method of claim 2 further comprising the step of electrolyzing waterto produce hydrogen to be stored in the step of storing hydrogen.
 4. Themethod of claim 3 further comprising the step of purifying the hydrogenproduced in the step of electrolyzing by removing water and otherimpurities from the hydrogen.
 5. The method of claim 1 wherein thesource of oxygen comprises air.
 6. The method of claim 3 wherein thestep of electrolyzing is carried out on-board a vehicle driven by aninternal combustion engine.
 7. The method of claim 6 further comprisingthe step of providing electrical power for the step of electrolyzingfrom an AC to DC converter that is powered from an alternator driven bythe engine.
 8. An apparatus for conditioning a catalyst within acatalytic converter from a cold start condition, the apparatuscomprising:a. a conditioning agent storage container for storing aquantity of a conditioning agent; b. a conduit coupling the conditioningagent storage container to the catalytic converter; and c. means forintroducing the conditioning agent to the catalytic converter prior tothe introduction of reactive organic gases or carbon monoxide to thecatalytic converter until the catalytic converter reaches lightofftemperature for carbon-containing compounds and, once the catalyticconverter has reached lightoff temperature, stopping the introduction ofthe conditioning agent to the catalytic converter, only at about thelightoff temperature of the catalytic converter.
 9. A system for thereduction of the cold-start emissions from an internal combustion enginewith an exhaust line and a catalytic converter in the exhaust linecomprising:a. hydrogen storage container for storing a quantity ofhydrogen; b. a fluid flow path coupling the hydrogen storage containerto the exhaust line; and c. a control valve in the fluid flow path todirect hydrogen into the catalytic converter prior to the introductionof reactive organic gases or carbon monoxide to the catalytic converteruntil the catalytic converter reaches lightoff temperature forcarbon-containing compounds and, once the catalytic converter hasreached lightoff temperature, to stop the introduction of theconditioning agent to the catalytic converter.
 10. The system of claim 9further comprising:a. a source of water; b. a electrolyzer coupled tothe source of water to electrolytically produce hydrogen; and c. a fluidflow path to direct hydrogen produced in the electrolyzer into thehydrogen storage container.
 11. The system of claim 10 furthercomprising a hydrogen purifier in the fluid flow path.
 12. The system ofclaim 11 wherein the hydrogen purifier comprises a water trap to removewater entrained with the hydrogen and an oxygen eliminator to removeoxygen contaminant that may be present with the hydrogen.
 13. The systemof claim 9 further comprising a source of air connected to the exhaustline.
 14. The system of claim 10 further comprising an alternator drivenby the internal combustion engine to develop AC power and an AC/DCconverter electrically coupled to the alternator to provide DC power tothe electrolyzer.
 15. An auxiliary system for an internal combustionengine having a fuel and air intake, combustion chambers, and anexhaust, the exhaust including a catalytic converter, the auxiliarysystem comprising:a. a hydrogen storage container; b. a control valvebetween the hydrogen storage container and the engine to selectivelyprovide hydrogen to the engine when the control valve is open; and c. aninternal combustion engine ignition control coupled to the control valveto open the control valve for a predetermined period of time during thestartup of the engine so that the engine is started with hydrogen untilthe catalytic converter reaches lightoff temperature forcarbon-containing compounds before the introduction of a hydrocarbon oroxygenated hydrocarbon fuel to the engine.
 16. The system of claim 15wherein the control valve is in fluid communication with the intake ofthe engine.
 17. The system of claim 15 wherein the control valve is influid communication with the cylinders of the engine.
 18. The system ofclaim 15 further comprising an electrolyzer connected to the hydrogenstorage container for the production of hydrogen to charge the hydrogenstorage container.
 19. A system for the reduction of the cold-startemissions from an internal combustion engine with an exhaust line and acatalytic converter in the exhaust line, the engine further having afuel and air intake and combustion chambers, the system comprising:a.hydrogen storage container; b. a fluid flow path coupling the hydrogenstorage container to the exhaust line to direct hydrogen into thecatalytic converter; c. a source of oxygen connected to the exhaustline; and d. a controllable port from the hydrogen storage container tothe engine wherein hydrogen from the storage container is ported to theengine for a controlled period of time during start-up of the engine sothat the engine is started with hydrogen until the catalytic converterreaches lightoff temperature for carbon-containing compounds beforc theintroduction of a hydrocarbon or oxygenated hydrocarbon fuel to theengine.
 20. The method of claim 1 wherein the catalyst comprisesa. amonolith of a first catalytic material, the monolith having an inletface; and b. a layer on the inlet face, the layer made of a secondcatalytic material that heats more rapidly in the presence of hydrogenand oxygen than the first catalytic material.
 21. The system of claim 9further comprising a catalytic converter including:a. a monolith of afirst catalytic material, the monolith having an inlet face; and b. alayer on the inlet face, the layer made of a second catalytic materialthat heats more rapidly in the presence of hydrogen and oxygen than thefirst catalytic material.
 22. The system of claim 19 further comprisinga catalytic converter including:a. a monolith of a first catalyticmaterial, the monolith having an inlet face; and b. a layer on the inletface, the layer made of a second catalytic material that heats morerapidly in the presence of hydrogen and oxygen than the first catalyticmaterial.
 23. The system of claim 10 wherein the source of watercomprises a vehicle's windshield-washer fluid reservoir.
 24. The systemof claim 21 wherein the electrolyzer comprises a plurality of cells. 25.The system of claim 22 wherein the electrolyzer comprises a plurality ofcells.
 26. A method of heating a catalyst in the exhaust system of aninternal combustion engine from a cold condition to light-offtemperature for carbon-containing compounds comprising the steps ofintroducing gaseous hydrogen and oxygen to the catalyst to inducespontaneous exothermic combination of the hydrogen and the oxygen by thecatalyst during startup of the internal combustion engine.
 27. Themethod of claim 26 further comprising the step of storing gaseoushydrogen within a hydrogen storage vessel prior to the step ofintroducing hydrogen.
 28. The method of claim 26 further comprising thestep of storing hydrogen as a metal hydride using a hydriding alloy inthe hydrogen storage vessel.
 29. The method of claim 27 furthercomprising the step of electrolyzing water to produce hydrogen to bestored in the step of storing hydrogen.
 30. The method of claim 26further comprising the step of storing gaseous oxygen within an oxygenstorage vessel prior to the step of introducing oxygen.
 31. The methodof claim 30 further comprising the step of electrolyzing water toproduce oxygen to be stored in the step of storing oxygen.
 32. Themethod of claim 29 further comprising the step of purifying the hydrogenproduced in the step of electrolyzing by removing water and otherimpurities from the hydrogen.
 33. The method of claim 26 wherein thesource of oxygen comprises air.
 34. The method of claim 26 wherein thesource of oxygen comprises oxygen produced by electrolysis on-board avehicle.
 35. The method of claim 29 wherein the step of electrolyzing iscarried out on-board a vehicle driven by an internal combustion engine.36. The method of claim 35 further comprising the step of providingelectrical power for the step of electrolyzing from an AC to DCconverter that is powered from an alternator driven by the engine.
 37. Amethod of heating a catalyst in the exhaust system of an internalcombustion engine from a cold condition to light-off temperature forcarbon-containing compounds comprising the steps of introducing gaseoushydrogen and oxygen to the surface of the catalyst to induce spontaneousexothermic combination of the hydrogen and the oxygen by the catalystafter startup of the internal combustion engine.
 38. The method of claim37 wherein the catalyst contains platinum or palladium.
 39. The methodof claim 37 further comprising the step of storing gaseous hydrogenwithin a hydrogen storage vessel prior to the step of introducinghydrogen.
 40. The method of claim 39 further comprising the step ofelectrolyzing water to produce hydrogen to be stored in the step ofstoring hydrogen.
 41. The method of claim 40 further comprising the stepof purifying the hydrogen produced in the step of electrolyzing byremoving water and other impurities from the hydrogen.
 42. The method ofclaim 37 wherein the source of oxygen comprises air.
 43. The method ofclaim 37 wherein the source of oxygen comprises oxygen produced byelectrolysis on-board a vehicle.
 44. The method of claim 40 wherein thestep of electrolyzing is carried out on-board a vehicle driven by aninternal combustion engine.
 45. The method of claim 44 furthercomprising the step of providing electrical power for the step ofelectrolyzing from an AC to DC converter that is powered from analternator driven by the engine.
 46. An apparatus for conditioning acatalyst within a catalytic converter in the exhaust system of aninternal combustion engine from a cold start condition, the apparatuscomprising:a. a hydrogen storage container for storing a quantity of ahydrogen; b. a conduit coupling the hydrogen storage container to thecatalytic converter; and c. means for introducing the hydrogen to thecatalytic converter during startup of the internal combustion engineuntil the catalytic converter reaches and maintains lightoff temperaturefor carbon-containing compounds.
 47. An apparatus for conditioning acatalyst within a catalytic converter in the exhaust system of aninternal combustion engine from a cold start condition, the apparatuscomprising:a. a hydrogen storage container for storing a quantity of ahydrogen; b. a conduit coupling the hydrogen storage container to thecatalytic converter; and c. means for introducing the hydrogen to thecatalytic converter after startup of the internal combustion engineuntil the catalytic converter reaches and maintains lightoff temperaturefor carbon-containing compound.
 48. An auxiliary system for an internalcombustion engine having a fuel and air intake, combustion chambers, andan exhaust line, the exhaust including a catalytic converter, theauxiliary system comprising:a. a hydrogen storage container; b. a firstcontrol valve between the hydrogen storage container and the engine toselectively provide hydrogen to the engine when the control valve isopen; c. a second control valve between the hydrogen storage containerand the exhaust; d. an internal combustion engine ignition controlcoupled to the second control valve to open the control valve for apredetermined period of time during the startup of the engine so thatthe engine is started with hydrogen; and e. a hydrogen control forintroducing the conditioning agent to the catalytic converter until thecatalytic converter reaches lightoff temperature for carbon-containingcompounds.
 49. The system of claim 48 further comprising:a. an oxygenstorage container; b. an oxygen flow path coupling the oxygen storagecontainer to the catalytic converter; and c. a control valve in theoxygen flow path for introducing oxygen from the oxygen storagecontainer to the catalytic converter simultaneously with theintroduction of hydrogen to the catalytic converter.
 50. The method ofclaim 3 wherein the step of electrolyzing water produceselectrochemically compressed hydrogen by the electrolyzer.
 51. Themethod of claim 1 further comprising the step of storing gaseous oxygenwithin an oxygen storage vessel prior to the step of introducing oxygen.52. The method of claim 51 further comprising the step of electrolyzingwater to produce oxygen to be stored in the step of storing oxygen. 53.The method of claim 52 further comprising the step of purifying theoxygen produced in the step of electrolyzing by removing water and otherimpurities from the oxygen.
 54. The method of claim 52 wherein the stepof electrolyzing water produces electrochemically compressed oxygen bythe electrolyzer.
 55. The method of claim 1 further comprising the stepof storing oxygen for introduction in the step of introducing oxygen.56. A system for the reduction of the cold-start emissions from aninternal combustion engine with an exhaust line and a catalyticconverter in the exhaust line comprising;(a) a hydrogen storagecontainer for storing a quantity of hydrogen; (b) an oxygen storagecontainer for storing a quantity of oxygen; (c) a first fluid flow pathcoupling the hydrogen storage container to the exhaust line to directhydrogen into the catalytic converter prior to the introduction ofreactive organic gases or carbon monoxide to the catalytic converteruntil the catalytic converter reaches lightoff temperature forcarbon-containing compounds; and (d) a second fluid flow path couplingthe oxygen storage container to the exhaust line to direct oxygen intothe catalytic converter with the hydrogen of step c.
 57. The system ofclaim 56 further comprising:a. a source of water; b. a electrolyzercoupled to the source of water to electrolytically produce hydrogen andoxygen; c. a hydrogen storage container to store the hydrogen producedby the electrolyzer; d. an oxygen storage container to store the oxygenproduced by the electrolyzer; e. means for directing the hydrogen fromthe hydrogen storage container and the oxygen from the oxygen storagecontainer into the exhaust line.
 58. The system of claim 57 furthercomprising an oxygen purifier coupled to the oxygen storage container.59. The system of claim 58 wherein the oxygen purifier comprises a watertrap to remove water entrained with the oxygen.
 60. The system of claim15 further comprising:a. an oxygen storage container; b. an electrolyzerconnected to the hydrogen storage container and the oxygen storagecontainer for the production of hydrogen to charge the hydrogen storagecontainer and oxygen to charge the oxygen storage container.
 61. Thesystem of claim 22 wherein at least one of said first and secondcatalytic materials includes platinum or palladium.
 62. The system ofclaim 10 wherein the source of water contains an antifreeze fluid inwhich water is miscible.